Darjes has been one of those philosophers who, while outwardly staying within the Wolffian school, have in truth distanced themselves from some key tenets of Wolff's system and taken their ideas to original directions. We have already seen Darjes suggest rather interesting innovations in his book on logic. If you know the field of German philosophy in the first half of 18th century, you won't be surprised to hear that his Latin book on same topic, Introductio in artem inveniendi seu logicam theoretico-practicam, is a much fuller treatment.
In a sense, most of the additions concern the necessary presuppositions of logic, that is, its metaphysical underpinnings. Like all the Wolffians thus far, Darjes considers certain key notions that we hold to be logical as ontological – for instance, the principle of contradiction is not a principle denying the affirmation and negation of the same proposition, but describes the ontological impossibility of incompatible things actualising at the same position. Darjes goes even further than other Wolffians, suggesting in a manner reminiscent of Russell that the subject-predicate -relation is not just a human convention, but reflects the order of reality itself.
Another interesting novelty in Darjesian ontology is that the basic ingredients of the reality are not so much individuals, but characteristics, of which individuals are then full combinations, to which no new characteristics can be added. Part of this ontological picture is the idea that some of these characteristics are atomic or not analysable to further characteristics. This picture resembles Wolffian idea of determinations, but seems ontologically stronger – Darjes takes characteristics to be things, if only partial ones.
Another interesting, if only a passing addition to the preface of logic, is Darjes's account of truth. As you might recall, with Wolff, truth in the logical sense was assigned a place only in the applied logic, because truth required relating the content of pure logic – concepts, judgements and syllogisms – to what they are supposed to represent. In a sense, Darjesian reorganisation is quite natural. With Darjes, as with all Wolffians thus far, logic is based on psychology, because concepts, judgements and syllogisms exist within human soul. Surely the relation of these logical items to what they represent is not a mere afterthought, but a necessary part of the psychology of human thinking underlying logic.
I have already described the most important novelties in the Darjesian logic itself in my description of its German version. This does not mean that his Latin logic would have nothing of interest, beyond the preface. One peculiar feature of Darjesian Latin logic book is its emphasis on invention, clearly expressed in the title of the work. Darjes is anxious to present not just theorems, but also solutions to problems – for instance, Darjes does not just define clear concepts, but also explains how to make one's concepts clearer. This is not a complete novelty, since we just saw Bilfinger doing something similar in his own logic.
Although sections on rules for disputations, communication of truths and hermeneutics are an addition in Darjes's Latin logic, they are not that peculiar in the more extensive context of logic textbooks. More interesting is the second part of Darjesian logic, which he calls dialectics, in separation from the part containing analytics. In effect, what Darjes means by dialectics is a study of probability and a search for probable truths – it is like reading part of Aristotelian logic through Bayesian eyes. What is even more intriguing is Darjes's idea of applying probability to pondering testimonies or to evaluating different hermeneutical possibilities.
This is just a glimpse of Darjes's innovations. Next time I shall again return to Wolff's natural law.